3rd generation partnership project (3GPP) long-term evolution (LTE) is a technology for enabling high-speed packet communications. Many schemes have been proposed for the LTE objective including those that aim to reduce user and provider costs, improve service quality, and expand and improve coverage and system capacity. The 3GPP LTE requires reduced cost per bit, increased service availability, flexible use of a frequency band, a simple structure, an open interface, and adequate power consumption of a terminal as an upper-level requirement.
Coordinated multi-point (CoMP) transmission and reception has been considered for 3GPP LTE Rel-11 as a tool to improve the coverage of high data rates, the cell-edge throughput, and also to increase system throughput. Downlink (DL) CoMP transmission implies dynamic coordination among multiple geographically separated transmission points (TPs). Uplink (UL) CoMP reception implies coordination among multiple, geographically separated points. Uplink CoMP reception can involve joint reception (JR) of the transmitted signal at multiple reception points and/or coordinated scheduling (CS) decisions among points to control interference and improve coverage.
Small cells using low power nodes are considered promising to cope with mobile traffic explosion, especially for hotspot deployments in indoor and outdoor scenarios. A low-power node generally means a node whose transmission power is lower than macro node and base station (BS) classes, for example pico and femto evolved NodeB (eNB) are both applicable. Small cell enhancements for evolved UMTS terrestrial radio access (E-UTRA) and evolved UMTS terrestrial radio access network (E-UTRAN) will focus on additional functionalities for enhanced performance in hotspot areas for indoor and outdoor using low power nodes.
One of potential solutions for small cell enhancement, dual connectivity has been discussed. Dual connectivity is used to refer to operation where a user equipment (UE) consumes radio resources provided by at least two different network points connected with non-ideal backhaul. Furthermore, each eNB involved in dual connectivity for a UE may assume different roles. Those roles do not necessarily depend on the eNB's power class and can vary among UEs. Dual connectivity may be one of potential solutions for small cell enhancement.
As the network becomes denser and smaller, the frequency of needed handover or switching of the cell may increase. The handover frequency may impact the overall UE throughput and quality of experience (QoE). Thus, to support efficient dense small cell operation, it is essential to enhance UE mobility handling such that a UE can freely move around a set of small cells without handover procedures or any radio resource control (RRC) reconfigurations which may lead relatively high overhead.